1. Field of the Invention
This invention relates generally to Global Positioning System (GPS) antennas and, in particular, this invention relates to a mounting bracket for a GPS antenna to be positioned on an aircraft.
2. Description of the Prior Art
Global Positioning System (GPS) is a space-based positioning and velocity system for determining the worldwide position and velocity of a craft, such as a wheeled or tracked vehicle, an amphibian, or watercraft. Global Positioning System has three major segments: space (transmitting satellites), control and user equipment (receiver). The GPS is predicated upon accurate and continuous knowledge of the spatial position of each satellite in the system, with respect to time and distance from a transmitting antenna to the user. Each satellite transmits its unique ephemeris data. This data is periodically updated by a master control station based upon information obtained from widely dispersed monitor stations. The GPS receiver automatically selects appropriate signals from the three or four satellites best in the field of view of the receiver based on optimum satellite-to-user geometry. The receiver then solves time of arrival difference quantities to obtain the distance between the user and satellites. This information establishes the user position with respect to the satellite system. A time correction factor then relates the satellite system. The user equipment measures four independent pseudo ranges and range rates and translates these to three-dimensional position and velocity information.
The receiver includes a standardized antenna mounted on the aircraft generally in a location on the airframe fuselage which will allow for the least airframe blockage and thus distortion of any incoming satellite transmitted signals. On fixed wing aircraft, the antenna should be mounted above the cabin near the front of the aircraft and as close to the centerline of the fuselage as possible. In addition, the GPS antenna should be mounted on a flat plane relative to the aircraft fuselage. This, in turn, provides optimum line of sight for the GPS antenna allowing GPS antennas to receive transmissions from GPS satellites without distorting incoming signals.
One prior art method for mounting a GPS antenna to a fixed wing aircraft required the user to drill antenna mounting holes and an electrical connector opening in the airframe of the aircraft, install the antenna and then use a sealant, such as RTV, to seal around the antenna base and the screw holes.
Another prior art apparatus and method of mounting a GPS antenna to a fixed wing aircraft required the user to use a large flat steel plate as the antenna support structure having an aperture therein, weld a stainless steel tube to the bottom of the antenna support structure which is aligned with the aperture, attach the GPS antenna to the antenna support structure using mounting screws and then secure the antenna support structure to the airframe by inserting the tube into the sextant port of the airframe so that the bottom portion of the tube including a pinning aperture extends into the interior the aircraft. A pin is inserted in the pinning aperture to secure the GPS antenna to the airframe.
These prior art apparatus and methods of securing a GPS antenna to fixed wing aircraft leave something to be desired in that it is undesirable to drill mounting holes within the airframe of the aircraft, the seals are susceptible to failure causing pressure loss within the aircraft, the antenna support structure may corrode and aerodynamic drag on the aircraft may increase and vibration or even breakage of the GPS antenna may occur. Such breakage of the GPS antenna renders the aircraft's Global Positioning System inoperable and requires the replacement of a GPS antenna which is expensive.